French beans - deficiency?

I have tried French beans for the first time this year. They were in a largish pot in compost.
They set off quite promising then started to fade to an unhealthy looking yellow colour and the amount of beans  and colour of them also went downhill quite quickly. I have fed them about once a week with comfrey tea after they flowered.
ON the photo is two sowings, the ones on the left are the ones that I have now given up on (I grubbed them up after taking the photo) THe one next to it is a second sewing - healthy at the moment, but I'd like to get a better crop this time.
ANy suggestions/reasons why they went so badly?

I agree - Dwarf French beans are usually planted out at about 6-8ins apart, there seems to be too many in the pot.

Climbers would need a much bigger pot to have any chance of success.

What does is say on the packet?

They should be described as climbing or dwarf (unless you bought them from Lidl who labelled my French climbers "runner beans"!) 

(Even though your first sowing look poorly, they don't seem to have made any attempt to climb, so my guess is "dwarf," although they are still too crowded whichever they are.)

The bottom leaves on my french beans have leaf yellowing or chlorosis.
I fed them with some sulphate of ammonia - it's actually labelled for this plant complaint.

It may be too late once they've gone yellow but they're still growing prolifically - the variety is 'Isabel'

Blood, Fish & Bone is the organic equivalent of Growmore